Hi Bill,
I will try to help a little but I have to talk in feet and inches. First, barometers are used as altimeters because as you increase your elevation, your station pressure is going to decrease. This happens at a rate of approximately 0.01 inhg/foot. Therefore, you need to calculate the elevation of your VP2 Console (where the barometric pressure is measured) to within about 10 feet if possible.
There are several ways to view "pressure". Your VP2 console will display "Sea Level Pressure", SLP, which factors in "Station Pressure", elevation, and humidity and temperature over the past 12 hours. Most cheaper personal weather stations provide "Altimeter Pressure" because it is instantaneous and takes no complex calculations.
HTH
George